Recent advances in cultivated epithelial transplantation

Currently, cultivated epithelial transplantation usually uses ex vivo-expanded epithelial cells, with or without biological carriers. Our group has carried out approximately 100 such procedures and has conducted research in this area. The results of a retrospective study indicate that cultivated limbal epithelial transplantation with amniotic membrane (AM) and airlifting may be beneficial at avoiding sight-threatening complications in patients with severe chronic cicatricial keratoconjunctivitis. Our experience in cultivated oral mucosal epithelial transplantation indicates that this technique is useful in achieving a stable ocular surface. However, the treatment for severe ocular surface diseases such as Stevens-Johnson syndrome remains unsatisfactory. In addition to using epithelial sheets with AM, we have developed a technique for generating carrier-free sheets using fibrin sealants. These sheets seem to contain more differentiated epithelium than those obtained with AM while retaining similar levels of colony-forming progenitor cells. A clinical trial of this technique is currently underway. We have also generated epithelial sheets using as biological carrier silk fibroin film, which offers a more transparent medium than conventional sheets. In terms of isolation and cultivation of corneal epithelial stem/progenitor cells, we found that single murine limbal cells exhibited clonal growth and generated stratified epithelial sheets. We also reported that hypoxic culture (2%) enhanced proliferation in human limbal epithelial cells while inhibiting differentiation. This technique may help maintain progenitor cells during ex vivo expansion of epithelial cells. Although these advances are expected to improve clinical outcomes in patients with ocular surface disorders, further improvements, such as the development of cultivation methods that do not require 3T3 feeder cells or real-time assessment of cultivated sheets, are required in the near future.